1. Field of the Invention
The application relates to a method utilized in a wireless communication and a communication device thereof, and more particularly, to a method of controlling packet switched data transmission in a wireless communication system and a related communication device.
2. Description of the Prior Art
In contrast to the circuit switched model of previous cellular systems (e.g. general packet radio service (GPRS), or universal mobile telecommunications system (UMTS)), LTE system has been designed to support only packet switched (PS) services. It aims to provide seamless Internet Protocol (IP) connectivity between a user equipment (UE) and a packet data network (PDN) via an evolved packet system (EPS) bearer for accessing Internet, as well as for running services such as Voice over IP (VoIP) provided by IP Multimedia Subsystem (IMS). The PDN is responsible for IP address allocation to the UE. An EPS bearer is typically associated with a QoS. Multiple EPS bearers can be established for a user in order to provide different QoS streams or connectivity to different PDNs. For example, a UE can be engaged in a VoIP call while at the same time browsing a web page or downloading a file transfer protocol (FTP) file.
Moreover, the EPS bearer is established via the EPS bearer context activation. In addition, the EPS bearer context can be either a default bearer context or a dedicated bearer context. A default EPS bearer context is activated when the UE requests a connection to a PDN in order to provide the UE with always-on IP connectivity to that PDN. A dedicated EPS bearer context is linked to a default EPS bearer context and represents additional EPS bearer resources between the UE and the PDN. In attach procedure in LTE, the UE sends ATTACH REQUEST message together with a PDN CONNECTIVITY REQUEST message contained in the EPS Session Management (ESM) message container information element to request PDN connectivity. When MME receives the ATTACH REQUEST message, the MME sends the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message together with ATTACH ACCEPT to activate a default EPS bearer to a PDN. Note that, EPS bearer context in LTE system is translated to a packet data protocol (PDP) context in UMTS or GPRS.
Consider a scenario that a user may pay a lot of money due to accidentally activating data transmission/reception in a UE in a roaming network. Therefore, the UE supporting GPRS or UMTS (e.g. high-speed downlink packet access (HSDPA)/high-speed uplink packet access (HSUPA)) provides a user interface (UI) for the user to enable or disable PS data access (i.e. enable/disable data transmission in roaming). The PS data access is disabled by forbidding any PDP context activation, and thereby the user can save money during roaming. However, if the UE is roaming to LTE network (i.e. Evolved Universal Terrestrial Radio Access Network (E-UTRAN)) which supports only PS services, and is not allowed to activate the PDP context or EPS bearer context (namely PS data access is disabled), the UE cannot perform PS data transmission, and a default bearer context is not allowed to be activated either. Therefore, the UE cannot originate a call by circuit switched (CS) fallback functionality, or initiate an IMS based call (e.g. normal IMS call or IMS emergency call).